We have identified a population of self-reactive intraepithelial lymphocytes (IEL) in the intestine of weanling mice that secretes IL2 without exogenous antigenic stimulation or a need for antigen presenting cells. Self-reactivity is mediated by a Vgamma1.1Cgamma4Vdelta6 T cell receptor (TCR) that is also expressed on self-reactive delta/gamma TCR+ T cell hybridomas derived from the thymus, spleen, liver and skin. Because peptides derived from a 60kd Mycobacterial heat shock protein (hsp 60) can enhance IL2 secretion by the Vgamma1.1Vdelta6 TCR-bearing hybridomas, it has been proposed that self reactivity results from the recognition of autologous murine hsp 60 on the hybrids' cell surface. In vivo, the expression of hsp60 is induced in damaged, infected or transformed cells, suggesting that self-reactive intestinal IEL may function in the antigen non-specific surveillance of the mucosal barrier by eliminating damaged enterocytes. The overall aim of this proposal is to determine the potential for self-reactive IEL to mediate immune surveillance and autoreactivity in the intestinal epithelium. The specific aims are 1) to identify and characterize self-reactive Vgamma1.1Cgamma4Vdelta6 T cells in vivo and 2) to identify the autoantigen and the molecular basis for its recognition. Since the original submission of this grant application we have prepared a Vgamma1- specific hamster anti-mouse monoclonal antibody that identifies this subset of gamma/delta T cells. We will use this antibody to study the ontogeny, distribution and function of Vgamma1+ IEL. To gain insight into the function of Vgamma1+ T cells in vivo we will also characterize Vgamma1 IEL induced after experimental infection with the coccidian parasite Eimeria or after immunization with heat shock proteins in vivo. In Aim II we will explore several different approaches to examine autoantigen recognition by this unique subset of T cells. Because self- reactive intestinal IEL have the potential to trigger or exacerbate autoimmune disease, an understanding of the molecular basis for the receptor/antigen interaction responsible for their activation may allow the development of new therapies for the inflammatory bowel diseases.